Tanning material



Patent ed Sept. 6 1938 UNITED STATES TANNING MATERIAE Alfred Russell and 'John w. Copenhaver, Philadelphia, Pa., assignors to Rohm & Haas Company,

Philadelphia, Pa.

No Drawing. Application October so, 1937, Serial No. 172,042

10 Claims.

This invention relates to the manufacture of tanning materials suitable for tanning pickled stock, for retanning leather already made by other means, and for bleaching or brightening chrome leather.

In our 'copending application, Serial No. 161,- 066, filed August 26, 1937, it is shown that excellent tanning materials especially suitable for the bleaching of chrome leather can be made by sulfonating a dihydroxy diaryl sulfone and condensing the resulting sulfone sulfonate with formaldehyde, We have now found that by co-condensing urea with the sulfone sulfonate and formaldehyde, a joint urea-sulfone sulfonate-formaldel5 hyde condensate is obtained that has certain advantages over the material obtained from the sulfone sulfonate and formaldehyde only. These advantages are particularly noticeable when the new tanning materials are used to bleach chrome stock. A better bleaching and brightening is obtained and the leather has a greater resistance to the action of sunlight.

In practicing the invention the dihydroxy diaryl sulfone sulfonate prepared by any suitable method, as for instance those disclosed in the above mentioned copending application, 'is dis- .solvedor diluted with water and to the solution urea is added and dissolved with the aid of heat if desired. The-temperature of the solution is then raised to a point at which the urea and sulfone will react with formaldehyde and the formaldehyde added slowly. When all the formaldehydehas been added the temperature is maintained at or near the boiling point of the solution until reaction is complete. It may then be cooled,

neutralized to the proper pH and diluted with water to the desired concentration.

The relative proportion of urea, sulfone sulfonate and formaldehyde that may be used varies 40 overs. wide range. The best ratio we have found is two molecular equivalents each of formaldehyde and sulfone sulfonate to one molecularequivalent of urea. These ratios we believe give on condensation a molecule having the formula wherein the R's represent similar or dissimilar dihydroxy diaryl sulfone sulfonates attached to v 9 the methylene groups by nuclear carbon atoms.

Reducing the quantity of urea decreases the quantity of this material in the final condensate but and only the maximum advantage of the invention lost by the reduction. The formaldehyde may be reduced to a lower limit of one mol. of formaldehyde for each two mols of sulfone sulfonate particularly when less than the best ratio i of urea to suifonate is used. An excess over this lower limit equivalent to the quantity of urea used is desirable. .A convenient rule to follow is to use at least one mol. of formaldehyde for each two mols of sulfone sulfonate plus one mol. of 5') formaldehyde for each mol. of urea.

Increasing the quantity of urea and/or formaldehyde above the best ratios above mentioned leads to the formation of more complicated molecules that also have tanning properties but no if further improvement is thereby obtained. How ever, if desired, up to four mols of formaldehyde and up to two mols of urea can be used with two mols of sulfone sulfonate.

The conditions of reaction such as temperature, 20 dilution, acidity, etc., are largely a matter of choice and affect the speed of the reaction more than the quality of the reaction product. We prefer to carry out the reaction at or about the boiling point of water and at the natural pH 25 of the sulfone sulfonate solution. Lower temperatures and high dilution slow the reaction and if the acidity becomes too high difficulty may be met in maintaining a suitably controlled rate of reaction. In the following examples, conditions of 30 reaction we have found convenient are illustrated but by a few simple tests other conditions equally suitable can be readily determined. In these examples the parts given are by weight.

Example 1.50 parts of 4:4 dihydroxy di- 35 phenyl sulfone is added to 70 parts of 98% sulfuric acid and the mixture heated-at 1i0-l20 C.

' for from 15 to 20 minutes or until a product enten minutes and the reaction mixture maintained v at 98-100 C. for four hours. It is then cooled somewhat, partly neutralized with 34 parts of caustic soda and diluted with water to a final.

mass of 520 parts.

Example 2. parts of 4:4 dihydroxy di-- 50 phenyl sulfone is sulfonated as in Example 1 using parts of 98% sulfuric acid. .6 parts of urea is dissolved in the sulfonation mixture and 51 parts of water added. The mixture is then heated to 98-100 C. and 20 parts of 30% aqueous formaldehyde added slowly over 10 minutes. The mixture is maintained at 98-100 C. and stirred continuously for three hours, then cooled, partly neutralized with 34 parts of caustic soda and diluted with water to a final mass of 520 parts.

The tanning materials'p'roduced' as in these examples may be used alone or in combination with other tanning materials in tanning skins or in retanning leather made byother tanning materials but their greatest value is found in their ability to bleach and brighten .chrome tanned leather. a white leather that has a resistance to sunlight even greater than that produced from tanning materials made from the sulfone'sulfonate and formaldehyde alone. Other dihydroxy diaryl sul fone sulfonates such as those in which one or both the phenyl groups of the diphenyl compound are substituted by one or more methyl or other alkyl groups may be substituted for the dihydroxy diphenyl sulfone sulfonate used in these examples.

In order to illustratethe use of these tanning materials to brighten chrome tanned leather the following example is given.

Example 3.-100 pounds of fully tanned chrome calfskin is drummed for an hour at F. with pounds of water and ten pounds, or other suitable quantity, of the tanning material prepared as described in Example 1; The stock is now washed with water till it shows a pH of 4-4 when it may be oiled arid finished in any recognized manner. The leather so produced has a white surface of remarkable resistance to the action of strong sunlight.

We claim:

1. The process of preparing a synthetic tanning material which comprises co-condensing a dihydroxy diaryl sulfone sulfonate and urea with formaldehyde.

2. The process of preparing a synthetic tanning material which comprises co-condensing a dihydroxy diphenyl sulfone sulfonate and urea with formaldehyde.

3. The process of preparing a synthetic tan- When used for this purpose they give ning material which comprises co-condensing 4:4 dihydroxy diphenyl sulfone sulfonate and urea with formaldehyde.

4. The process of preparing a synthetic tanning material which comprises co-condensin substantially two molecular equivalents of a dihydroxy diphenyl sul'fone sulfonate and substantially one molecular equivalent of urea and substantially two molecular equivalents of formaldehyde.

5. A synthetic tanning material which in the acidic form consists of the joint condensation product of a dihydroxy diaryl sulf one sulfonate and urea with formaldehyde.

6. A synthetic tanning material which in the acidic form consists of the joint condensation product of a dihydroxy diphenyl sulfone sulfonate and urea with formaldehyde.

7. A synthetic tanning material which in the acidic form consists of the joint condensation product of 4:4 dihydroxy diphenyl sulfone sulfonate and urea with formaldehyde.

8. A synthetic tanning material which in the acidic form consists of the joint condensation products of substantially two molecular equivalents of a dihydroxy diphenyl sulfone sulfonate and substantially one molecular equivalent of urea and substantially two molecular equivalents of formaldehyde.

9. In the process of making leather the improvement which comprises treating a. chrome tanned leather with a joint condensation product of a. dihydroxy diphenyl sulfone sulfonate, urea and formaldehyde.

10. In the process of making leather the improvement which comprises treating a chrome tanned leather with a joint condensation product of substantially two molecular equivalents of a dihydroxy diphenyl sulfone sulfonate, substantially one molecular equivalent of urea, and substantially two molecular equivalents of formaldehyde.

ALFRED RUSSELL. JOHN W; COPENHAVER. 

